Similarly, breast cancer cell lines can also be distinguished by their hormone receptor expression, with phenotypes similar to the clinical counterpart (e.g., TNBC breast cancer cell lines are highly metastatic in mouse models, readily colonizing the lung or bone marrow after intravenous inoculation, while ER+ MCF7 cells do not readily colonize and exhibit slow or no growth in distant metastatic sites following inoculation [73,79]). The gene discussed is ESR1; the disease is breast cancer.